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. Author manuscript; available in PMC: 2022 Dec 1.
Published in final edited form as: Curr Opin Insect Sci. 2021 Oct 25;48:79–88. doi: 10.1016/j.cois.2021.10.003

Figure 2: Crispr/Cas9 mediated genome editing.

Figure 2:

An engineered single guide RNA (brown sequence) binds to the Cas9 enzyme and recognizes a specific sequence (green sequence) in the target DNA complementary to the guide RNA and immediately adjacent to the PAM sequence (red). The Cas9 enzyme will generate a double strand break four base pairs (bp) from the PAM sequence. The double strand break will be repaired by one of two mechanisms: 1) non-homologous end-joining (NHEJ, left pathway), which can cause a small insertion or deletion (InDel) if repair is incorrect, or 2) homology directed repair (HDR, right pathway) which requires a repair template with homology on both ends immediately adjacent to the cut site. Through homologous recombination anywhere in the flanking sequence the repair template can integrate a transgene sequence (surrounded by the homology arms) into the cut site. This pathway allows knocking DNA into the genome. If two guide RNAs are used, the repair process can replace an existing sequence in the genome with the transgene sequence.